Even if he had never published a note of his own music, nor laid a hand on a keyboard in public, Olivier Messiaen's influence on the course of music in the second half of the 20th century would still have been indelible. As a teacher at the Paris Conservatoire for more than 35 years, first as a professor of harmony and analysis, and later, as professor of composition, his students included many of the composers - Pierre Boulez, Jean Barraqu&eacute, Karlheinz Stockhausen, Iannis Xenakis - who reshaped musical language after the second world war. They were followed by leading figures from subsequent generations, too, such as Gérard Grisey, Tristan Murail, and George Benjamin.

It was Messiaen's own achievement as a composer that gave him unique authority as a teacher. His body of work was forged out of his own early experience as an organist and the French tradition to which he was an heir. To this, perhaps encouraged by his teacher, Paul Dukas, he added modernist elements from Debussy and Stravinsky. And it's Messiaen's music, with its heady mixture of sensuality and the certainty of his Roman Catholic faith, informed by wonder at the glories of the natural world, that is being celebrated this year for his centenary.

Placing Messiaen and his works accurately on the crowded map of 20th-century music is difficult, though. If there were aspects of his music that regularly touched on some of the century's trends and "isms" - and in a few key works of the late 1940s, he seemed to point the direction in which Boulez, Stockhausen and their contemporaries would lead the avant garde in the following decade - his own development proceeded in a totally individual and fundamentally inimitable fashion. Messiaen's pupils never composed like their teacher, because no one else could have brought together such a variety of musical influences - Greek modes and Hindu rhythms, plainchant and birdsong - and fused them convincingly into such a personal and instantly recognisable style.

The popular Messiaen works - the Quartet for the End of Time, the massive Turangalîla Symphony and the devotional piano cycle Vingt Regards sur l'Enfant-Jésus - were all composed in the 1940s, yet he ended the decade with two extraordinary piano pieces, the Four Studies and Canteyodjaya, that brought him briefly into alignment with the avant garde.

Through the 1950s he followed an individual and unexpected path. Though birdsong had first appeared in his music more than 15 years earlier, he now began to study and incorporate it far more systematically, transcribing it meticulously in the field and for a while basing his works almost exclusively upon it. This cloistered immersion in the natural world seems to have been Messiaen's response to a personal crisis, both emotional and spiritual - it's surely significant that the 1950s was the only extended period in his composing career when his music contained no explicit religious references. It has also been suggested that birdsong became his way of evading responsibility for the musical revolution he had unwittingly triggered in his radical piano pieces, and whose subsequent development into total serialism he found hard to accept.

The best of those 1950s works - the two piano-and-ensemble scores Oiseaux Exotiques and Réveil des Oiseaux, the collection of piano pieces brought together in the seven books of the Catalogue des Oiseaux and, at the end of the decade, the greatest of all his orchestral works, Chronochromie - are some of the most remarkable musical achievements of that time. The works that followed in the 1960s and 70s, when Messiaen's faith had evidently been restored (and when, crucially, he was finally able to marry his former student, the pianist Yvonne Loriod, following the death of his first wife) built upon those pieces in an increasingly monumental way.

Yet the biggest and least expected of all Messiaen's scores was still to come. In 1983 his opera Saint Francois d'Assise received its first performance in Paris. If the subject matter - the life of the Roman Catholic church's favourite saint - was predictable enough, so was the work's static quality, as a series of tableaux depicting important events in St Francis's life, which brings it far closer to sacred oratorio than to living, breathing music theatre. For despite its occasional depictions of the apocalypse and its moments of high grandeur, Messiaen's music never aimed at achieving any goal other than that of celebrating his faith or hymning the wonders of the animate and inanimate world around him.

The lack of forward momentum that was fundamental to his harmonic systems, rhythms and melodies is what sets Messiaen apart not only from his contemporaries but from almost the whole of the western art-music tradition of the previous 500 years. Without his explorations of timelessness and his new ways of looking at how musical time passes, many of the works of Boulez, Birtwistle, Ligeti and other leading composers of our time would be unthinkable. It is music that produces strong reactions on both sides, but it is music that is going to endure.

The essential Messiaen on CD

La Nativité du Seigneur

Gillian Weir (Priory)

The nine meditations from 1935 are the most frequently performed of the great organ cycles.

Quartet for the End of Time

Shaham/Meyer/Wang/Chung (DG)

Messiaen's only major chamber work, composed in 1940-41 while he was interned in a prison camp in Silesia.

Vingt Regards sur l'Enfant-Jésus

Steven Osborne (Hyperion, two CDs)

One of the landmarks in 20th-century piano music, and a summation of Messiaen's musical language in the 1940s.

Turangalîla Symphony

Royal Concertgebouw Orch/Chailly (Decca)

Music of huge power and saccharine kitsch that you either love or loathe.

Chronochromie; Et Exspecto Resurrectionem Mortuorum

Cleveland Orch/Boulez (DG)

Extraordinary products of the 1960s, conducted by the greatest of all Messiaen's pupils.

Des Canyons aux Etoiles

French Radio Philharmonic Orch/Chung (DG, two CDs)

A depiction of the American south-west and the birds that inhabit it.

· From the Canyons to the Stars: The Music of Olivier Messiaen opens at the Southbank Centre, London, on February 2, and runs all year. Box office: 0871-663 2500.